Some floors are comprised of concrete footings and slabs. The footings are set in the ground, and the slabs rest on both the footings and the ground. Water tables and temperature changes cause the ground under the slab to expand and contract. This ground pressure causes the slab to move vertically. This movement of the slab is known as heaving. The footings remain relatively stable because they are set deeper in the ground. As a result, the slabs tends to heave more dramatically in their center away from any footings.
Some walls are comprised of vertical studs that are connected at the top and bottom by horizontal runners. Typically, the studs and runners are two inch by four inch wooden boards that are nailed together. The studs and runners are usually covered by a surface, such as dry wall or sheet rock.
When the slab heaves, walls that rest on the slab are pushed up. These are typically non-loadbearing walls. This action transmits a powerful amount of stress to the wall and to the overall structure. This situation is compounded by the fact that the stable footings do not experience heaving and tend to pull the structure back towards the ground. This creates even greater stress. This stress often manifests itself in cracked ceilings, uneven floors, and sticking doors.
A current solution is to leave a gap between the studs and the runners of non-loadbearing walls. The stud is still nailed to the runner, but a gap is left between the surface of the stud and the surface of the runner so that the nails span the gap. When the wall is pushed up, the studs can simply slide up on the nails. If the wall recedes, the stud slides back down the nails. This situation is depicted in FIG. 1 which has been designated as prior art.
This solution is lacking. Aesthetically, it looks shoddy. More importantly, the nails spanning the gap are often bent or crushed as the wall is stressed. This weakens the wall since the stud is no longer properly secured to the runner. The gap can also cause the wall to hang from the top runner by nails. This is not an effectively secure connection for a hanging wall. A connector is needed to allow the studs some vertical movement in response to heaving, but to maintain a secure connection to the runners.
One known metal connector is an "L" bracket that has holes through one flange for a rigid connection with nails to a board, and the other flange has a slot allowing the other board to be flexably connected with a nail. The bracket is used to allow a roof to float above a wall that sags, however, this connector is deficient for use in the above context. Because it is only an "L" shape it does not restrict movement of the members in all the directions the invention does. The "L" bracket allows members to twist and bend in several directions. This connector is not designed to correct the problem solved by the invention.